Author ORCID Identifier
0000-0002-5152-3122
Document Type
Dissertation
Date of Award
5-31-2024
Degree Name
Doctor of Philosophy in Chemical Engineering - (Ph.D.)
Department
Chemical and Materials Engineering
First Advisor
Edward L. Dreyzin
Second Advisor
Mirko Schoenitz
Third Advisor
Xianqin Wang
Fourth Advisor
Mengqiang Zhao
Fifth Advisor
Demitrios Stamatis
Abstract
Interactions of powders with high-temperature plasma and shockwaves occur in diverse scenarios, such as nuclear blasts, accidental industrial dust explosions, solid propellant combustion in explosive charges and when removing contaminants from surfaces. Electrostatic Discharge (ESD), known for generating shock and plasma, is a promising lab-scale technique for simulating these interactions. Studies with ESD involved placing powders near a spark-producing gap between electrodes and observing mechanical and chemical processes like particle motion and ignition. A limited range of spark conditions and material properties have been tested, which facilitated the development and validation of preliminary computational models describing this system. Significant gaps in understanding shock/plasma-powder interactions in the ESD system remained. The effects of broader range of particle sizes and shape were unclear. Reported studies used monolayers or powders in shallow cavities for simplicity, but more defined loading configurations are needed for practical scenarios. Furthermore, the mechanisms behind morphological changes in ejected powders, like melting and agglomeration, and the efficiency of mass removal for cleaning applications, are not fully understood. Additionally, there is a lack of data related to velocities of vertical motion of particles of different sizes lifted by ESD at microsecond timescales.
This dissertation develops experiments to study powder interactions with lab-scale shock and plasma, aiming to enhance computational models for extreme environments like fireballs. Various powders are used, with mechanical milling employed to produce particles with customized compositions, shapes and sizes. Sample holders with cavities with varied depths held the powders, and optical and x-ray imaging methods observed motion of lifted particles. Mass of powder removed by a single spark is quantified and powders collected post-exposure are examined. Results show ESD's effectiveness in removing powders across a range of sizes and densities between 1-100 gm and 2.5-8.9 g/cc, respectively. A single ESD pulse removes almost all powder from a shallow 0 2 mm deep cavity, while the removal efficiency reduces with increasing cavity depth. Factors like particle size, ESD energy, and electrode proximity influenced particle lifting and ignition, with spherical powders lifted by the ESD more efficiently. Initial particle ejection speeds can reach or exceed 10 m/s, with later-ejected particles moving slower. Lift forces created by steep gas velocity gradients immediately above the powder layer primarily cause ejection, as shown by the present experimental data consistently with theoretical predictions. The dissertation also identifies timescales for transient agglomerate formation and particle melting, highlighting areas where the future model improvements are desired.
Recommended Citation
Mukhopadhyay, Shomik, "Interaction of particles with plasma and shock produced by pulsed spark discharge" (2024). Dissertations. 1759.
https://digitalcommons.njit.edu/dissertations/1759
Included in
Aerodynamics and Fluid Mechanics Commons, Ceramic Materials Commons, Electrical and Electronics Commons, Explosives Engineering Commons, Heat Transfer, Combustion Commons, Thermodynamics Commons
